Evaluation of toxicity indicators in rat primary astrocytes, C6 glioma and human 1321N1 astrocytoma cells: can gliotoxicity be distinguished from cytotoxicity?

A comparison was made of rat primary astrocytes, C6 glioma cells pre-treated with dibutyryl cyclic AMP, and the human astrocyte 132N1 cell line using a range of 40 compounds and the neutral red (NR) assay. The 40 chemicals included substances known to be toxic to astrocytes or neurons, to be generally cytotoxic or not thought to be toxic to nervous tissue. For those compounds which were toxic, changes in glial fibrillary acidic protein (GFAP) levels were measured in the primary and C6 cultures, and changes in vimentin and S-100 measured in the C6 cells. The number of compounds with EC50 values < 2000 microg/ml for the NR assay for the different cell cultures were as follows: primary astrocytes, 19; C6 cells, 15; and 1321N1 cells, 11. The log of the EC50 values for the NR assay for the test compounds between the three cell types was not significantly different at the 5% level by paired Student's t-test. For the toxic substances the correlation coefficients of the EC50 values between primary cells and the C6 or 1321N1 cells were r > 0.5, and between the C6 and 1321N1 cells r > 0.9. For GFAP there was a similar degree of correlation in EC50 values between the different cell types. The GFAP, vimentin and S-100 levels showed similar EC50 values for the toxicants, but were not as sensitive as the NR assay. The toxic substances caused altered morphology in the primary, C6 and 1321N1 cells, with increased branching of cell processes. The combined astrocyte systems identified 8 out of 9 substances reported to be toxic to astrocytes in vivo, together with substances which have general cytotoxic properties. A number of substances (including the 1 out of 9 reported gliotoxic substances), which may primarily affect neurons, which may affect nervous tissue after long-term exposure, or which are not thought to be toxic to nervous tissue, were not detected. The astrocyte systems positively identify gliotoxic and cytotoxic substances and will allow detailed mechanistic studies to be made on the different underlying mechanisms.     

Diabetic foot ulcers: prevention, diagnosis and classification

Diabetic ulcers are the most common foot injuries leading to lower extremity amputation. Family physicians have a pivotal role in the prevention or early diagnosis of diabetic foot complications. Management of the diabetic foot requires a thorough knowledge of the major risk factors for amputation, frequent routine evaluation and meticulous preventive maintenance. The most common risk factors for ulcer formation include diabetic neuropathy, structural foot deformity and peripheral arterial occlusive disease. A careful physical examination, buttressed by monofilament testing for neuropathy and noninvasive testing for arterial insufficiency, can identify patients at risk for foot ulcers and appropriately classify patients who already have ulcers or other diabetic foot complications. Patient education regarding foot hygiene, nail care and proper footwear is crucial to reducing the risk of an injury that can lead to ulcer formation. Adherence to a systematic regimen of diagnosis and classification can improve communication between family physicians and diabetes subspecialists and facilitate appropriate treatment of complications. This team approach may ultimately lead to a reduction in lower extremity amputations related to diabetes.     

The grain size dependence of the yield,flow and fracture stress of commercial purity silver

Heavily cold-rolled sheet material of 99.9 pct purity Ag has been recrystallized at varying temperatures to give average grain diameters,l, in the range between 1 and 60 μ. For this material, the yield stress, flow stress at several strain values, and fracture stress follow the Hall-Petch relation: $$\sigma _\varepsilon = \sigma o_\varepsilon + k_\varepsilon l^{ - 1/2} $$ whereσ _ε is the flow stress at a particular value of strain, ε, ands _{o ε} andk _ε are the experimental constants appropriate to a particular strain value. The range in grain size obtained for this material was sufficiently large to determine that silver can be appreciably strengthened by grain size refinement and that several other relations previously suggested to relate the stress and grain size could be discounted. The finest grain sizes were measured from replicas of etched specimens as viewed with the electron microscope. It is proposed that this type of grain size strengthening may be responsible for the exceptional strength which occurs in certain films of silver fabricated by vapor deposition techniques.     

Cardiovascular and thermal consequences of protective clothing: a comparison of clothed and unclothed states

We have undertaken a laboratory-based examination of the cardiovascular and thermal impact of wearing thermal (heat) protective clothing during fatiguing exercise in the heat. Seven males completed semi-recumbent, intermittent cycling (39.6 degrees C, 45% relative humidity) wearing either protective clothing or shorts (control). Mean core and skin temperatures, cardiac frequency (f(c)), stroke volume (Q), cardiac output (Q), arterial pressure, forearm blood flow (Q(f)), plasma volume change, and sweat rates were measured. In the clothed trials, subjects experienced significantly shorter times to fatigue (52.5 vs. 58.9 min), at lower peak work rates (204.3 vs. 277.4 W), and with higher core (37.9 degrees vs. 37.5 degrees C) and mean skin temperatures (37.3 degrees vs. 36.9 degrees C). There was a significant interaction between time and clothing on f(c), such that, over time, the clothing effect became more powerful. Clothing had a significant main affect on Q, but not Q, indicating the higher Q was chronotropically driven. Despite a greater sweat loss when clothed (923.0 vs. 547.1 g.m(-2) x h(-1); P<0.05), Q(f) and plasma volume change remained equivalent. Protective clothing reduced exercise tolerance, but did not affect overall cardiovascular function, at the point of volitional fatigue. It was concluded that, during moderately heavy, semi-recumbent exercise under hot, dry conditions, the strain on the unclothed body was already high, such that the additional stress imparted by the clothing ensemble represented a negligible, further impact upon cardiovascular stability.     

Modelling the VO2 kinetic response to heavy intensity exercise in children

The purpose of this study was to apply a series of mathematical models in order to investigate the nature of the kinetic response to heavy intensity exercise with children and identify a suitable model with which to estimate parameters of the response. Sixty two children (35 male, 27 female aged 10-15 years) completed four transitions from baseline pedalling to 40% of the difference between their previously determined anaerobic threshold and peak VO2 on an electronically braked cycle ergometer. Initially three models were fitted to the averaged response profiles following the end of phase 1. and their residuals compared; 1, a single exponential with a delay term; 2, an exponential and linear term with independent delays; and 3, a double exponential with independent delays. Up to 95% of the response profiles were better fitted by either model 2 or 3 (p < 0.05), and model 3 was a statistically better fit (p < 0.05) than model 2 in 77% of cases. Residual inspection confirmed the superior fit by model 3. A fourth model which consisted of a single exponential with a delay term was fitted within the phase 2 fitting window. Estimated parameters (A1 and tau1), using model 4 were not significantly different from model 3, and model 4 was identified as the model of choice due to the wide confidence intervals in tau2 and A2 using model 3. It was concluded that the nature of the response to heavy intensity exercise in children is similar to that previously reported with adults and that the response should be modelled accordingly.     

Chiral ionic liquids as stationary phases in gas chromatography

Recently, it has been found that room-temperature ionic liquids can be used as stable, unusual selectivity stationary phases. They show "dual nature" properties, in that they separate nonpolar compounds as if they are nonpolar stationary phases and separate polar compounds as if they are polar stationary phases. Extending ionic liquids to the realm of chiral separations can be done in two ways: (1) a chiral selector can be dissolved in an achiral ionic liquid, or (2) the ionic liquid itself can be chiral. There is a single precedent for the first approach, but nothing has been reported for the second approach. In this work, we present the first enantiomeric separations using chiral ionic liquid stationary phases in gas chromatography. Compounds that have been separated using these ionic liquid chiral selectors include alcohols, diols, sulfoxides, epoxides, and acetylated amines. Because of the synthetic nature of these chiral selectors, the configuration of the stereogenic center can be controlled and altered for mechanistic studies and reversing enantiomeric retention.     

Determination of cell viability in single or mixed samples using capillary electrophoresis laser-induced fluorescence microfluidic systems

The advent of high-efficiency microbial separations will have a profound effect on both chemistry and microbiology. For the first time, it appears that it may be possible to obtain qualitative and quantitative information on microbial systems with the accuracy, precision, speed, and throughput that currently is found for chemical systems. Recently it was suggested that an analytical separations-based approach for determining the viability of cells would be advantageous. The feasibility of such an approach is demonstrated using CE-LIF of two bacteria and yeast. The analytical procedures and figures of merit are outlined. High-throughput analyses and evaluation of microorganisms now appear to be possible.